Lin Wan is an ordinary white-collar worker who rents in the old "Echo Apartment" - this tube building built in the 1980s is famous for "the residents can clearly hear each other's echoes", but there is no shortage of tenants.
A month ago, after the 12th resident disappeared mysteriously, a strange saying began to circulate in the apartment: Every time at 12 o'clock in the night, the elevator would stop one more time on the 13th floor - a floor that did not exist at all.
Lin Wan accidentally pressed the button one night and was involved in a serial mystery that spanned ten years. Missing residents, hidden surveillance videos, the secrets behind each tenant, and her own gradually blurred memory... The truth is far scarier than the ghosts.
